Method, apparatus and system for supporting non-vector line

ABSTRACT

Embodiments of the present invention provide a method, an apparatus, and a system for supporting a non-vector line. The method includes: selecting n non-vector lines T L  from lines that are in an initializing stage, where n is an integer greater than or equal to 1; controlling to perform no further initializing for other lines that are in the initializing stage except the T L  until the T L  fully enters a data transmission stage; and before the T L  enters the data transmission stage, estimating a far-end crosstalk coefficient C TL-SV  from the T L  to a vector line S V  that is in the data transmission stage, where the C TL-SV  is used in signal processing to eliminate far-end crosstalk caused by the T L  to the S V .

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2011/077675, filed on Jul. 27, 2011, which is hereby incorporatedby reference in its entirety.

TECHNICAL FIELD

Embodiments of the present invention relate to the data communicationfield, and in particular, to a method, an apparatus and a system forsupporting a non-vector line in a vectored-DSL system.

BACKGROUND

A digital subscriber line (xDSL) is a high-speed data transmissiontechnique on an unshielded twisted pair (UTP). FIG. 1 shows a systemreference model of a system DSL access multiplexer DSLAM (DSL AccessMultiplexer) that provides multiple xDSL access.

Due to electromagnetic induction, mutual interference occurs betweenmultiple signals of DSLAM access, which is called crosstalk. As shown inFIG. 2, near-end crosstalk NEXT (Near-End Crosstalk) energy and far-endcrosstalk FEXT (Far-End Crosstalk) energy increase with the increase ofthe frequency. Frequency division multiplexing is applied to xDSL uplinkand downlink channels, and near-end crosstalk does not cause too muchharm to system performance. However, when wider and wider bands areapplied to xDSL, far-end crosstalk affects transmission performance ofthe line more seriously.

Currently, a vectored-DSL (vectored-DSL) technology is put forward inthe industry. It primarily takes advantage of the possibility of jointtransmitting and receiving on a DSLAM side and uses a signal processingmethod to cancel FEXT interference and finally eliminate FEXTinterference in each signal. FIG. 3 and FIG. 4 illustrate workingscenarios of synchronous transmitting and synchronous receiving on theDSLAM side respectively.

In vectored-DSL, a downlink precoding matrix P and an uplinkcancellation matrix W need to be estimated. In a vectored-DSL system,the following steps are performed:

1. Sync symbol (Sync Symbol) alignment is implemented, where the syncsymbol is a DMT symbol synchronization signal that carries asynchronization frame.

2. A vectoring control entity VCE (Vectoring Control Entity) allocatespilot sequences to all lines in a unified manner and an ONU-side VDSL2transceiver unit at the Optical network unit (VTU-O) of each linejointly modulates the pilot sequence, which are allocated by the VCE, onthe Sync Symbols of all lines.

3. The receiver side feeds back an error to the VCE.

The downlink precoding matrix P and the uplink cancellation matrix W canbe estimated in the VCE first, and then the vectoring technology isapplied to cancel the FEXT. The downlink precoding matrix is also knownas a downlink crosstalk cancellation matrix or a downlink far-endcrosstalk coefficient, and the uplink cancellation matrix is also knownas an uplink crosstalk cancellation matrix or an uplink far-endcrosstalk coefficient.

A process of initializing a new line that joins in (Join in) ordinarynon-vectored VDSL2 lines or vectored-DSL vector lines in the prior artincludes handshake (Handshake), channel discovery (Channel Discovery),training (Training), and channel analysis and exchange (Channel Analysisand Exchange). After initializing is finished, a data transmission(Showtime) stage comes. The Channel Discovery stage of an ordinarynon-vectored VDSL2 line further includes an O-P-Channel-Discovery 1stage and an R-P-Channel-Discovery 1 stage; and the Training stagefurther includes an O-P-Training 1 stage and an R-P-Training 1 stage.For the initializing of the vectored-DSL vector line, before the datatransmission (Showtime) stage, an O-P-VECTOR 1 stage and an R-P-VECTOR 1stage are inserted in the Channel Discovery stage, and an O-P-VECTOR 1-1stage, an O-P-VECTOR 2-1 stage, an R-P-VECTOR 1-1 stage, an R-P-VECTOR1-2 stage, and an R-P-VECTOR 2 stage are inserted in the Training stage.Within such stages, all and/or part of the downlink precoding matrix Pand uplink cancellation matrix W may be estimated.

The vectored-DSL is a very-high-speed digital subscriber line 2 (VDSL2)for far-end self-crosstalk elimination. Because the VDSL2 technology isearlier than the vectored-DSL technology and has been applied widely,the upgrade from the VDSL2 to the vectored-DSL must allow for support oflegacy lines, that is, ordinary non-vectored VDSL2 lines. A customerpremises equipment (CPE) of a legacy line is a VDSL2 legacy CPE thatdoes not support the vectored DSL. However, the VDSL2 legacy CPE doesnot support sending and receiving of a pilot sequence and feedback of anerror on the Sync Symbol, which makes it difficult for the VCE toestimate the uplink and downlink far-end crosstalk coefficients intendedfor cancelling the crosstalk caused by the legacy line onto the vectorline. If some lines in the system are in the data transmission(Showtime) stage, when a legacy line joins in the system, in the casethat the crosstalk from the legacy line is not cancelled, the bit errorsof the vector line in the Showtime stage will increase due to a lowersignal-to-noise ratio (SNR), or even the vector line in the Showtimestage is deactivated and retrained. As a latent uncertain factor, thelegacy line seriously affects the rate of the vector line and thestability of the entire vectored-DSL system.

If all VDSL2 legacy CPEs in the VDSL2 of the live network are upgradedto or replaced with vectored-DSL enabled vector customer premisesequipment VDSL2 vector CPE, huge costs are required. Some old legacyCPEs may not be upgradable to the vector CPE for various reasons such asno support of error calculation, error feedback, or uplink sending ofpilot sequences, which makes it necessary to replace the entire CPE andfurther increases costs.

As regards the issue of the vectored-DSL being down-compatible with thelegacy CPE, a vector friendly (vector Friendly) CPE solution is putforward in the industry. Specifically, the solution specifies that thevector Friendly CPE must be able to identify and receive a pilot signalmodulated on a downlink Sync Symbol, and additionally, a VTU-O controlsdownlink Sync Symbol alignment of all lines. When the vectored-DSLsystem meets the above two conditions, for the vector line, the VCE canestimate a downlink cancellation coefficient for cancelling legacy linecrosstalk. In this way, the potential stability trouble caused by thelegacy line onto the vector line in the entire vectored-DSL system iseliminated in the downlink direction. In the application of the vectorFriendly solution, the legacy CPE in the live network still needs to beupgraded to the vector Friendly CPE, which requires a high cost. Becausethe vector Friendly CPE is unable to send uplink pilot signals, the VCEcan hardly estimate the far-end crosstalk coefficient intended forcancelling the crosstalk caused by the legacy line in the uplinkdirection onto the vector line. Consequently, the potential stabilitytrouble caused by the legacy line onto the vector line in thevectored-DSL system is not eliminated in the uplink direction.

SUMMARY

Embodiments of the present invention aim to solve the followingtechnical problem: supporting a VDSL2 legacy CPE of a live network in avectored-DSL system, and eliminating impacts caused by a legacy lineconnected to the VDSL2 legacy CPE, which is a non-vector line, ontostability of a vector line in the entire vectored-DSL system, that is,eliminating far-end crosstalk caused by the legacy line onto the vectorline.

In one aspect, an embodiment of the present invention provides a methodfor supporting a non-vector line, including:

selecting n non-vector lines T_(L) from lines that are in aninitializing stage, where n is an integer greater than or equal to 1;

controlling to perform no further initializing for other lines that arein the initializing stage except the T_(L) until the T_(L) fully entersa data transmission stage; and

before the T_(L) enters the data transmission stage, estimating afar-end crosstalk coefficient C_(TL-SV) from the T_(L) to a vector lineS_(V) that is in the data transmission stage, where the C_(TL-SV) isused in signal processing to eliminate far-end crosstalk caused by theT_(L) to the S_(V).

In another aspect, an embodiment of the present invention provides anapparatus for supporting a non-vector line, including:

a non-vector line selecting unit, configured to select n non-vectorlines T_(L) from lines that are in an initializing stage, where n is aninteger greater than or equal to 1;

a non-vector line initializing controlling unit, configured to controlto perform no further initializing for other lines that are in theinitializing stage except the T_(L) until the T_(L) fully enters a datatransmission stage; and

a non-vector line far-end crosstalk coefficient estimating unit,configured to estimate, before the T_(L) enters the data transmissionstage, a far-end crosstalk coefficient C_(TL-SV) from the T_(L) to avector line S_(V) that is in the data transmission stage, where theC_(TL-SV) is used in signal processing to eliminate far-end crosstalkcaused by the T_(L) to the S_(V).

In another aspect, an embodiment of the present invention provides asystem for supporting a non-vector line, including:

a VCE, at least two lines, and an VTU-O, where: the at least two linesinclude at least one vector line and at least one non-vector line, andthe at least two lines are connected to the VTU-O and controlled by theVTU-O, where the at least one vector line is connected to acorresponding ONU-side vector transceiver unit VTU-O-v and controlled bythe VTU-O-v, and the at least one non-vector line is connected to acorresponding ONU-side vector transceiver unit VTU-O-l and controlled bythe VTU-O-l;

the VCE selects n non-vector lines T_(L) from lines that are in aninitializing stage, where n is an integer greater than or equal to 1;

the VCE controls ONU-side vector transceiver units corresponding toother lines that are in the initializing stage except the T_(L), so asto perform no further initializing for the other lines until the T_(L)fully enters a data transmission stage; and

before the T_(L) enters the data transmission stage, the VCE estimates afar-end crosstalk coefficient C_(TL-SV) from the T_(L) to a vector lineS_(V) that is in the data transmission stage, where the C_(TL-SV) isused in signal processing to eliminate far-end crosstalk caused by theT_(L) to the S_(V).

In the embodiments of the present invention, a vectored-DSL system cansupport existing VDSL legacy CPEs in a live network without upgradingthe VDSL2 legacy CPEs in the live network of VDSL2, and, by controllinginitializing of a vector CPE and a legacy CPE in an orderly way, cancelthe crosstalk from the legacy line to the vector line in the downlinkdirection, cancel the crosstalk from the legacy line to the vector linein the uplink direction to the utmost, and therefore, massively relievepotential stability troubles caused by the legacy line to the vectorline in the entire vectored-DSL system.

BRIEF DESCRIPTION OF DRAWINGS

To illustrate the technical solutions in the embodiments of the presentinvention more clearly, the following briefly introduces theaccompanying drawings required for describing the embodiments.Apparently, the accompanying drawings in the following description showmerely some embodiments of the present invention, and a person ofordinary skill in the art may still derive other drawings from theseaccompanying drawings without creative efforts.

FIG. 1 is an xDSL system reference model;

FIG. 2 is a line crosstalk model;

FIG. 3 is a schematic diagram of joint sending on a DSLAM side andseparate receiving on a user side;

FIG. 4 is a schematic diagram of joint receiving on a DSLAM side andseparate sending on a user side;

FIG. 5 is a schematic diagram of flowchart of supporting a non-vectorline according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of flowchart of supporting a non-vectorline according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of flowchart of supporting a non-vectorline according to an embodiment of the present invention;

FIG. 8 is a schematic diagram of processing of supporting a non-vectorline according to an embodiment of the present invention;

FIG. 9 is a schematic diagram of state change in supporting a non-vectorline according to an embodiment of the present invention;

FIG. 10 is a schematic diagram of processing of supporting a non-vectorline according to an embodiment of the present invention;

FIG. 11 is a schematic diagram of state change in supporting anon-vector line according to an embodiment of the present invention;

FIG. 12 is a schematic diagram of an apparatus for supporting anon-vector line according to an embodiment of the present invention;

FIG. 13 is a schematic diagram of system interfaces according to anembodiment of the present invention;

FIG. 14 is a schematic diagram of flowchart of estimating a far-endcrosstalk coefficient from a non-vector line to a vector line accordingto an embodiment of the present invention;

FIG. 15 is a schematic diagram of an apparatus for estimating a far-endcrosstalk coefficient according to an embodiment of the presentinvention;

FIG. 16 is a schematic diagram of a VTU-O according to an embodiment ofthe present invention;

FIG. 17 is a schematic diagram of a VTU-O according to an embodiment ofthe present invention; and

FIG. 18 is a schematic diagram of cancelling downlink crosstalkaccording to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

The following clearly describes the technical solutions in theembodiments of the present invention with reference to the accompanyingdrawings in the embodiments of the present invention. Apparently, thedescribed embodiments are merely a part rather than all of theembodiments of the present invention. All other embodiments obtained bya person of ordinary skill in the art based on the embodiments of thepresent invention without creative efforts shall fall within theprotection scope of the present invention.

Non-vector lines in the embodiments of the present invention are legacyordinary VDSL2 lines, including existing lines that use a VDSL2 customerpremises equipment CPE that does not support sending and receiving ofpilot sequences and feedback of an error sample on a Sync Symbol.

In the embodiments of the present invention, symbols in Table 1 are usedto represent lines in different stages. S_(V) represents a vector linein the Showtime stage, S_(L) represents a legacy line in the Showtimestage, J_(V) represents a vector line in the initializing (Initializing)stage, J_(L) represents a legacy line in the Initializing stage, Vrepresents all vector lines including S_(V) and J_(V), and L representsall legacy lines including S_(L) and J_(L). The symbols in Table 1 maybe regarded as representing the corresponding line sets, respectively.

TABLE 1 Showtime Join in In the data transmission stage In theinitializing stage Vector line set S_(V) J_(V) Legacy line set S_(L)J_(L)

An embodiment of the present invention provides a method for supportinga vector line, as shown by 500 in FIG. 5, including:

501. A VCE selects n non-vector lines T_(L) from lines that are in aninitializing stage, where n is an integer greater than or equal to 1.

503. The VCE controls to perform no further initializing for other linesthat are in the initializing stage except the T_(L) until the T_(L)fully enters a data transmission stage.

505. Before the T_(L) enters the data transmission Showtime stage, theVCE estimates a far-end crosstalk coefficient C_(TL-SV) from the T_(L)to a vector line S_(V) that is in the data transmission stage, where theC_(TL-SV) is used in signal processing to eliminate far-end crosstalkcaused by the T_(L) to the S_(V).

A person skilled in the art understands that the far-end crosstalkcoefficient refers to a downlink far-end crosstalk coefficient or anuplink far-end crosstalk coefficient, or both a downlink far-endcrosstalk coefficient and an uplink far-end crosstalk coefficient. Forease of description, the far-end crosstalk coefficient mentioned belowrefers to the above three circumstances, and readers can judge whetherit denotes a downlink far-end crosstalk coefficient or an uplink far-endcrosstalk coefficient, or both a downlink far-end crosstalk coefficientand an uplink far-end crosstalk coefficient according to the context.

In 503, the VCE controls to perform no further initializing for otherlines that are in the initializing stage except the T_(L). If otherlines include non-vector lines, the VCE may control the VTU-O not tosend a handshake signal to the non-vector lines; or, control the VTU-Oto prevent the non-vector lines in other lines from entering a channeldiscovery stage or staying in the channel discovery stage; if otherlines include vector lines, the VCE may control the VTU-O not to send ahandshake signal to other vector lines that are in the initializingstage; or, control the VTU-O corresponding to other vector lines thatare in the initializing stage, so as to prevent other vector lines inthe initializing stage from entering the channel discovery stage orstaying in the channel discovery stage. For the T_(L) line, the VCE maycontrol the VTU-O to send a handshake signal to the T_(L) line, or makethe T_(L) enter the channel discovery stage or stay in the channeldiscovery stage, so as to continue with the T_(L) line initializingprocess.

The T_(L) should include a proper number of lines, that is, n should beset to a proper value, to ensure that, before all lines in the T_(L)enter the Showtime, a vector line can send enough Sync Symbols andsearch for the corresponding Error Samples to estimate the far-endcrosstalk coefficient from lines in a subset T to the vector line. Theenough Sync Symbols may be 4 to 5 Sync Symbols. In theory, the ErrorSamples of 4 to 5 Sync Symbols are enough for estimating thecancellation coefficient from the 4 to 5 lines to other vector linesthat are in the Showtime stage. In view of the impact caused by noiseonto accuracy of the estimated value of the cancellation coefficient,the proper number of lines in the T_(L) may be 1 to 5 so as to ensureaccuracy of the estimated value of the cancellation coefficient. If thenon-vector lines are initialized one by one, in theory, the vector lineneeds to send only one Sync Symbol, which is enough for estimating thefar-end crosstalk coefficient from the current separately initializedline to the vector line.

Further, the far-end crosstalk coefficient C_(TL-SV) from the T_(L) tothe vector line S_(V) that is in the data transmission stage may beestimated in only the channel discovery stage of the T_(L) initializingprocess; or, the far-end crosstalk coefficient C_(TL-SV) from the T_(L)to the vector line S_(V) that is in the data transmission stage may beestimated twice in the channel discovery stage and the training stagerespectively of the T_(L) initializing process. The downlink far-endcrosstalk coefficient from the T_(L) to the S_(V) may be estimated in anO-P-Channel-Discovery 1 stage of the Channel Discovery stage, and theuplink far-end crosstalk coefficient from the T_(L) to the S_(V) linemay be estimated in an R-P-Channel-Discovery 1 stage. The downlinkfar-end crosstalk coefficient from the T_(L) to the S_(V) may also bere-estimated in an O-P-Training 1 stage, and the uplink far-endcrosstalk coefficient from the T_(L) to the S_(V) line may be estimatedin an R-P-Training 1 stage.

Further, in estimating a far-end crosstalk coefficient C_(TL-SV) fromthe T_(L) to a vector line S_(V) that is in the data transmission stage,the method shown in FIG. 14 may be applied, including: performing nocontrol on alignment between a sync symbol of the non-vector line and async symbol of the vector line, and receiving a frequency domain signalexistent on the T_(L) and corresponding to a time point of the syncsymbol of the vector line, where the signal is obtained when no controlis performed on whether the sync symbol of the non-vector line isaligned with the sync symbol of the vector line; receiving an errorsample of the sync symbol of the S_(V), where the error samplecorresponds to the signal; and using the signal and the error sample tocalculate the C_(TL-SV), where the S_(V) may be all or part of thevector lines in the data transmission stage.

As can be seen from the above embodiment, some non-vector lines areselected for initializing, and no further initializing is performed forother lines in the process of initializing the selected non-vectorlines, thereby controlling orderly initializing of legacy lines in anorderly manner. In addition, the interference caused by initializing ofother lines to the initializing of the selected line is reduced, andbetter estimation results are obtained in estimating the far-endcrosstalk coefficient. By using the crosstalk cancellation coefficientfrom the non-vector line to the vector line estimated in theinitializing process, the far-end crosstalk caused by the non-vectorline to the vector line is eliminated to the utmost, thereby reducingvector-DSL system instability caused by the legacy lines to the utmost,and realizing support for compatibility with the legacy non-vectorlines.

The method for supporting a non-vector line may further include steps inFIG. 6, including:

601. The VCE controls to initialize at least one vector line T_(V) inthe lines that are in the initializing stage. The T_(V) may be all orpart of the vector lines that are currently in the initializing stage.

603. Before the T_(V) enters the data transmission stage, the VCEestimates a far-end crosstalk coefficient C_(SL-TV) from the non-vectorline S_(L) that is in the data transmission stage to the T_(V) and afar-end crosstalk coefficient C_(TV-TV) between the lines Tv, where theC_(SL-TV) is used in signal processing to eliminate far-end crosstalkcaused by the S_(L) to the T_(V), and the C_(TV-TV) is used in signalprocessing to eliminate far-end crosstalk between the lines Tv.

The foregoing steps may be performed before or after the steps shown inFIG. 5.

Further, the estimating, by the VCE, a far-end crosstalk coefficientC_(SL-TV) from the non-vector line S_(L) that is currently in the datatransmission stage to the T_(V) and a far-end crosstalk coefficientC_(TV-TV) between the lines Tv in 603, may be performed in the trainingstage of the T_(V) initializing process. The downlink crosstalkcancellation coefficient from the S_(L) to the T_(V) and the downlinkcrosstalk cancellation coefficient between the lines Tv may be estimatedin the O-P-VECTOR 2-1 stage, and the uplink crosstalk cancellationcoefficient from the S_(L) to the T_(V) and the uplink crosstalkcancellation coefficient between the lines Tv may be estimated in theR-P-VECTOR 2 stage.

Further, when the VCE estimates the far-end crosstalk coefficientC_(TV-TV) between the lines Tv in 603, the VCE may estimate the downlinkcrosstalk cancellation coefficient between the lines Tv in theO-P-VECTOR 2-1 stage; estimate the uplink crosstalk cancellationcoefficient between the lines Tv in the R-P-VECTOR 1 stage, re-estimatethe uplink crosstalk cancellation coefficient between the lines Tv inthe R-P-VECTOR 1-1 stage, and re-estimate the uplink crosstalkcancellation coefficient between the lines Tv in the R-P-VECTOR 1-2stage; and estimate or re-estimate the uplink crosstalk cancellationcoefficient between the lines Tv in the R-P-VECTOR 2 stage.

Further, the method shown in FIG. 14 may be applied in estimating thefar-end crosstalk coefficient C_(SL-TV) from the S_(L) to the T_(V) in603, including: performing no control on whether a sync symbol of thenon-vector line is aligned with a sync symbol of the vector line,receiving a frequency domain signal existent on the S_(L) andcorresponding to a time point of the sync symbol of the vector line;receiving an error sample of the sync symbol of the T_(V); and using thesignal and the error sample to calculate the C_(SL-TV).

As can be seen from the above embodiment, by sequentially initializingthe vector lines and the non-vector lines, newly joining in lines arecontrolled to undergo the initializing process in an orderly manner. Inaddition, by estimating the far-end crosstalk coefficient from thenon-vector line that is in the data transmission stage to the vectorline in the process of initializing the vector line, and using theestimated far-end crosstalk coefficient to eliminate the far endcrosstalk, the far-end crosstalk caused by the non-vector line to thevector line is eliminated to the utmost, thereby reducing vector-DSLsystem instability caused by the legacy lines to the utmost, andrealizing support for compatibility with the legacy non-vector lines.

Further, considering the impact caused by the vector line S_(V) that isin the data transmission stage, the method for supporting a non-vectorline may further include the steps shown in FIG. 7:

701. Before the T_(V) enters the data transmission stage, the VCEestimates a far-end crosstalk coefficient C_(TV-SV) from the T_(V) tothe vector line S_(V) that is in the data transmission stage and afar-end crosstalk coefficient C_(SV-TV) from the S_(V) to the T_(V),where the C_(TV-SV) is used in signal processing to eliminate far-endcrosstalk caused by the T_(V) to the S_(V), and the C_(SV-TV) is used insignal processing to eliminate far-end crosstalk caused by the S_(V) tothe T_(V).

Further, that the VCE estimates the far-end crosstalk coefficientC_(TV-SV) from the T_(V) to the vector line S_(V) that is currently inthe data transmission stage and the far-end crosstalk coefficientC_(SV)-T_(V) from the S_(V) to the T_(V) in 701 may be that the VCEestimates the downlink crosstalk cancellation coefficient from the T_(V)to the S_(V) in the O-P-VECTOR 1 stage, re-estimates the downlinkcrosstalk cancellation coefficient from the T_(V) to the S_(V) in theO-P-VECTOR 1-1 stage, estimates the downlink crosstalk cancellationcoefficient from the S_(V) to the T_(V) in the O-P-VECTOR 2-1 stage,estimates the uplink crosstalk cancellation coefficient from the T_(V)to the S_(V) and can estimate the uplink crosstalk cancellationcoefficient from the S_(V) to the T_(V) line in the R-P-VECTOR 1 stage,re-estimates the uplink crosstalk cancellation coefficient from theT_(V) to the S_(V) and can re-estimate the uplink crosstalk cancellationcoefficient from the S_(V) to the T_(V) line in the R-P-VECTOR 1-1stage, re-estimates the uplink crosstalk cancellation coefficient fromthe T_(V) to the S_(V) and can re-estimate the uplink crosstalkcancellation coefficient from the S_(V) to the T_(V) line in theR-P-VECTOR 1-2 stage, and estimates or re-estimates the uplink crosstalkcancellation coefficient from the S_(V) to the T_(V) line in R-P-VECTOR2.

FIG. 8 shows an example of supporting a non-vector line according to anembodiment of the present invention, including the following steps:

801. The VCE determines line sets S_(V), S_(L), J_(V), and J_(L).

At a specific time point, each line set in each stage may be determinedfirst. Each of the four sets may be empty, but at least one of J_(V) andJ_(L) is not empty. In the example in FIG. 8, it is assumed that none ofthe four sets is empty. According to this embodiment, a person skilledin the art can easily obtain the processing procedure in the case thatone set or certain sets are empty. In this embodiment, it is assumedthat after the S_(V), the S_(L), the J_(V), and the J_(L) are determinedin 801 and before the initializing of all lines in the J_(L) is finishedin 804, no new line joins in within the period. In the Handshake stage,the VTU-R interacts with the VTU-O to know whether their capabilitiessupport vector CPEs or legacy CPEs. Therefore, before the Handshakestage, the VCE does not know whether the CPE connected thereto is avector CPE, and in the Handshake stage, the VCE knows the type of theCPE through the VTU-O, and therefore, knows the type of the line.

802. The VCE controls the VTU-O connected to the J_(V) to continueinitializing the J_(V). After initializing of the J_(V) is finished andbefore the J_(V) enters the Showtime stage, the VCE estimates thefar-end crosstalk coefficient from the J_(V) to the S_(V), the far-endcrosstalk coefficient from the S_(V) to the J_(V), the far-end crosstalkcoefficient from the S_(L) to the J_(V), and the far-end crosstalkcoefficient from the J_(V) to the J_(V), that is, the far-end crosstalkcoefficient between the J_(V) lines. The J_(V) enters the datatransmission stage after initializing is finished.

In the period after the initializing is continued for the J_(V) andbefore the J_(V) enters the Showtime stage, the VTU-O connected to theJ_(L) is controlled to obstruct initializing of the J_(L) line, that is,to perform no further initializing for the J_(L) line. If the S_(L) isempty, the far-end crosstalk coefficient from the S_(L) to the J_(V)does not need to be estimated.

803. Update the line set S_(V) to a union set of the original S_(V) andJ_(V). At this time, the J_(V) becomes an empty set.

804. The VCE controls the VTU-O connected to the J_(L) to continueinitializing the lines in the J_(L). A subset T of the J_(L) may beselected, and further initializing for the T is performed under control.Before the T enters the Showtime stage, the far-end crosstalkcoefficient from the T to the S_(V) is estimated, and the T changes thestate to enter the Showtime stage after initializing is finished. In theperiod after initializing is continued for the T and before the T entersthe Showtime, other lines in the J_(L) are obstructed, that is, nofurther initializing is performed for other lines in the J_(L) until theT fully enters the Showtime stage. After initializing of the T isfinished, the line set S_(L) is updated to a union set of the S_(L) andthe T determined in 801, and the line set J_(L) is updated to a set withthe T removed from the original J_(L). If other lines still exist in theJ_(L), the foregoing process in this step is repeated until the J_(L)becomes an empty set.

To ensure the effect of initializing, the subset T selected each timeshould include a proper number of lines, and preferably, include 1 to 5lines.

In 802, the far-end crosstalk coefficient from the J_(V) line to theS_(V) line may be estimated first, and then other far-end crosstalkcoefficients are estimated, so as to prevent the S_(V) from bit errorsor other errors or even line interruption due to J_(V) crosstalk.

In estimating the far-end crosstalk coefficient from the non-vector lineto the vector line in 804, algorithms such as a least mean square errorLMS algorithm, a matrix first-order likelihood algorithm, or a matrixinversion algorithm may be applied.

The following describes specific application of the estimated far-endcrosstalk coefficient by using the scenario of supporting a non-vectorline in FIG. 8 as an example. After the far-end crosstalk coefficientfrom the J_(V) line to the S_(V) line is estimated in 802, the S_(V)line can enable a downlink precoder and/or an uplink canceller from theJ_(V) line to the S_(V) line.

For the downlink direction, the following precoding may be performed:{tilde over (x)} _(VS) =P _(VS-VS) x _(VS) +P _(LS-VS) x _(LS) +P_(VJ-VS) x _(VJ)

where P_(VS-VS) is an existing downlink far-end crosstalk coefficientbetween the S_(V) lines, x_(VS) is an S_(V) line signal input into theprecoder, P_(LS-VS) is an existing downlink far-end crosstalkcoefficient from the S_(L) line to the S_(V) line, x_(LS) is an S_(L)line signal input into the precoder, P_(VJ-VS) is a downlink far-endcrosstalk coefficient from the J_(V) line to the S_(V) line as estimatedin 802, x_(VJ) is a J_(V) line signal input into the precoder, andx_(VS) is a signal output by the precoder after the S_(V) line signalpasses through the precoder.

For the uplink direction, the following uplink crosstalk cancellationmay be performed:{tilde over (y)} _(VS) =W _(VS-VS) y _(VS) +W _(LS-VS) y _(LS) +W_(VJ-VS) y _(VJ)

where W_(VS-VS) is an existing uplink far-end crosstalk coefficientbetween the S_(V) lines, y_(VS) is an S_(V) line signal input into thecanceller, W_(LS-VS) is an existing uplink far-end crosstalk coefficientfrom the S_(L) line to the S_(V) line, y_(LS) is an S_(L) line signalinput into the canceller, W_(VJ-VS) is an uplink far-end crosstalkcoefficient from the J_(V) line to the S_(V) line as estimated in 802,y_(VJ) is a J_(V) line signal input into the canceller, and {tilde over(y)}_(VS) is a signal output by the canceller after the S_(V) linesignal passes through the canceller.

After the far-end crosstalk coefficient from the S_(V) line and theJ_(V) line to the J_(V) line and the cancellation coefficient from theS_(L) line to the J_(V) line are estimated in 802, the J_(V) lineenables downlink precoders and/or uplink cancellers from the S_(V) lineto the J_(V) line, from the J_(V) line to the J_(V) line, and from theS_(L) line to the J_(V) line.

For the downlink direction, the following precoding may be performed:{tilde over (x)} _(VJ) =P _(VS-VJ) x _(VS) +P _(LS-VJ) x _(LS) +P_(VJ-VJ) x _(VJ)

where P_(VS-VJ) is a downlink far-end crosstalk coefficient from theS_(V) line to the J_(V) line as estimated in 802, x_(VS) is an S_(V)line signal input into the precoder, P_(LS-VJ) is a downlink far-endcrosstalk coefficient from the S_(L) line to the J_(V) line as estimatedin 802, x_(LS) is an S_(L) line signal input into the precoder,P_(VJ-VJ) is a downlink far-end crosstalk coefficient from the J_(V)line to the J_(V) line as estimated in 802, x_(VJ) is a J_(V) linesignal input into the precoder, and {tilde over (x)}_(VJ) is a signaloutput by the precoder after the J_(V) line signal passes through theprecoder.

For the uplink direction, the following crosstalk cancellation may beperformed:{tilde over (y)} _(VJ) =W _(VS-VJ) y _(VS) +W _(LS-VJ) y _(LS) +W_(VJ-VJ) y _(VJ)

where W_(VS-VJ) is an uplink far-end crosstalk coefficient from theS_(V) line to the J_(V) line as estimated in 802, y_(VS) is an S_(V)line signal input into the canceller, W_(LS-VJ) is an uplink far-endcrosstalk coefficient from the S_(L) line to the J_(V) line as estimatedin 802, Y_(LS) is an S_(L) line signal input into the canceller,W_(VJ-VJ) is an uplink far-end crosstalk coefficient from the J_(V) lineto the J_(V) line as estimated in 802, y_(VJ) is a J_(V) line signalinput into the canceller, and {tilde over (y)}_(VJ) is a signal outputby the canceller after the J_(V) line signal passes through thecanceller.

After the far-end crosstalk coefficient from the line in the subset T tothe line in the V is estimated in 804, the line in the V enables aprecoder and/or an uplink crosstalk canceller from the line in the T tothe line in the V. For the downlink direction, the applied precoder isas follows:{tilde over (x)} _(V) =P _(V-V) x _(V) +P _(LS-V) x _(LS) +P _(T-V) x_(T)

where P_(V-V) is a downlink far-end crosstalk coefficient between the Vlines, and may be obtained according to the existing P_(VS-VS) and theestimated P_(VS-VJ), P_(VJ-VS), and P_(VJ-VJ); P_(LS-V) is a downlinkfar-end crosstalk coefficient from the S_(L) line to the V line, and isobtained according to the existing P_(LS-VS) and the estimatedP_(LS-VJ); P_(T-V) is a downlink far-end crosstalk coefficient from theT line to the V line as estimated in 804; x_(V), x_(LS), and x_(T) arerespectively line signals in the V, the S_(L), and the T input in theprecoder; and {tilde over (x)}_(V) is a signal output by the precoderafter the V line signal passes through the precoder.

For the uplink direction, the following crosstalk cancellation may beperformed:{tilde over (y)} _(V) =W _(V-V) y _(V) +W _(LS-V) y _(LS) +W _(T-V) y_(T)

where W_(V-V) is an uplink far-end crosstalk coefficient between the Vlines, and may be obtained according to the existing W_(VS-VS) and theestimated W_(VJ-VJ), W_(VS-VJ), and W_(VJ-VS); W_(LS-V) is an uplinkfar-end crosstalk coefficient from the S_(L) line to the V line, and maybe obtained according to the existing W_(LS-VS) and the estimatedW_(LS-VJ); W_(T-V) is an uplink far-end crosstalk coefficient from the Tline to the V line as estimated in 803; y_(V), y_(LS), and y_(T) arerespectively line signals in the V, the S_(L), and the T input in thecanceller; and {tilde over (y)}_(V) is a signal output by the cancellerafter the V line signal passes through the canceller.

In 802, an LMS algorithm is used to estimate the far-end crosstalkcoefficient from the S_(V), the S_(L), and the J_(V) to the J_(V); or,based on errors in multiple occasions of vector line feedback, a formulain the form of the following matrix is applied, where each column in Xand E represents one occasion of sending a signal and the correspondingerror:E _(VJ) =H _(VS-VJ) X _(VS) +H _(VJ-VJ) X _(VJ) +H _(LJ-VJ) X _(LJ) +N_(VJ).

Noticeably, the E_(VJ), the X_(VS), the X_(VJ), and the X_(LJ) are knownand the N_(VJ) is very small, maximum likelihood estimation or aleast-square method may be applied to estimate the far-end crosstalkcancellation coefficient from the S_(V), the S_(L), and the J_(V) to theJ_(V); or another algorithm is applied to the estimation.

In 804, an LMS algorithm is used to estimate the cancellationcoefficient from the T to the S_(V); or, based on errors in multipleoccasions of vector line feedback, a formula in the form of thefollowing matrix is applied, where each column in X and E represents oneoccasion of sending a signal and the corresponding error:E _(VS) =H _(VS-VS) P _(VS-VS) X _(VS) +H _(LS-VS) P _(LS-VS) X _(LS) +H_(T-VS) X _(T) +N _(VS).

Similarly, the E_(LS), the X_(VS), the X_(LS), and the X_(T) are knownand the N_(LS) is very small, maximum likelihood estimation or aleast-square method may be applied to estimate the cancellationcoefficient from the T to the S_(V); or another algorithm is applied tothe estimation.

When the foregoing method is applied, a good crosstalk cancellationcoefficient from the legacy line to the vector line can be obtained evenif the Sync Symbol of the legacy line is not aligned with the SyncSymbol of the vector line; and, when the Sync Symbol of some legacylines is aligned with the Sync Symbol of the vector lines, second bestcrosstalk cancellation coefficients from the legacy line to the vectorline can also be obtained.

The VCE can implement a state machine to control initializing for newlines to support non-vector lines. The lines in the Showtime stage atany time constitute a set S, and new lines that are currently in theInitializing stage constitute a set J, where S includes a vector lineset S_(V) and a legacy line set S_(L), and J includes a vector line setJ_(V) and a legacy line set J_(L). The VCE may perform state transitionin a way shown in FIG. 9:

When the VCE is in the S1 state, the VCE updates the current state ofthe J regularly or irregularly, and performs state transition accordingto the state of the J: if the J is an empty set, that is, no linecurrently joins in and waits for getting online, the S1 state remains;if the J_(V) is not an empty set, that is, the J includes a vector line,the state changes to the S2 state; if the J_(V) is an empty set and theJ_(L) is not an empty set, that is, the J includes only legacy lines,the state changes to the S3 state.

As can be seen from the foregoing judgment for state transition, in theprocessing of the state machine, when a vector line and a legacy linethat are in the Initializing state coexist, the vector line isinitialized first.

When the VCE is in the S2 state, the vector line in the Initializingstage is initialized. In the initializing process, a new line may joinin and need to be initialized. State transition may be performedaccording to the state of the J in the current system each time afterinitializing of at least one vector line is finished: if the J is anempty set, the state changes to the S1 state; if the J_(V) is not anempty set, the S2 state remains; and, if the J_(V) is an empty set andthe J_(L) is not an empty set, the state changes to the S3 state.

When the VCE is in the S3 state, the legacy line in the Initializingstage is initialized. In the initializing process, a new line may joinin and need to be initialized. State transition may be performedaccording to the state of the J in the current system each time afterinitializing of at least one legacy line is finished: if the J is anempty set, the state changes to the S1 state; if the J_(V) is not anempty set, the state changes to the S2 state; and, if the J_(V) is anempty set and the J_(L) is not an empty set, the S3 state remains.

The following describes the state machine in FIG. 9 with reference to aspecific example:

After the system starts running, at the t0 time, no line joins in, andthe state machine runs in the S1 state; and, at the t1 time, if a newline joins in, the value of the J_(V) changes to J_(V1), and the valueof the J_(L) changes to J_(L1), and therefore, the state changes to S2.

In the S2 state, the VTU-O corresponding to the J_(V1) lines may becontrolled so that the J_(V1) lines continue the initializing processsimultaneously or consecutively. Here it is assumed that theinitializing process is continued simultaneously. After initializing isfinished, all J_(V1) lines enter the Showtime stage. For the J_(L1)lines, in the period after the initializing process is continued for theJ_(V1) lines simultaneously and before all J_(V1) lines enter theShowtime stage, the VTU-O corresponding to the J_(L1) lines iscontrolled to obstruct the initializing process of the J_(L1) lines.

If a vector line S_(V1) in the Showtime stage already exists in thesystem at the t1 time, in the process of initializing the J_(V1), thefar-end crosstalk coefficient C_(JV1-SV1) from the J_(V1) to the vectorline S_(V1) that is currently in the data transmission stage, thefar-end crosstalk coefficient C_(SV1-JV1) from the S_(V1) to the J_(V1),and the far-end crosstalk coefficient C_(JV1-JV1) between the J_(V1)lines may be estimated. The J_(V1) enters the data transmission stageafter initializing is finished. The C_(JV1-SV1) is used in signalprocessing to eliminate the far-end crosstalk caused by the J_(V1) tothe S_(V1), the C_(SV1-JV1) is used in signal processing to eliminatethe far-end crosstalk caused by the S_(V1) to the J_(V1), and theC_(JV1-JV1) is used in signal processing to eliminate the far-endcrosstalk between the J_(V1) lines.

If a non-vector line S_(L1) in the Showtime stage already exists in thesystem at the t1 time, in the process of initializing the J_(V1), thefar-end crosstalk coefficient C_(SL1-JV1) from the S_(L1) to the J_(V1)can be estimated in the process of initializing the J_(V1), where theC_(SL1-JV1) is used in signal processing to eliminate the far-endcrosstalk caused by the S_(L) to the J_(V).

In the process of initializing the J_(V1), no other lines areinitialized. Therefore, the vector lines and the legacy lines in theShowtime stage in the system do not change until initializing of theJ_(V1) lines is finished and the J_(V1) lines enter the Showtime stage.

After initializing of the J_(V1) lines is finished and the J_(V1) linesenter the Showtime stage, as against the t1 time, at the t2 time, theJ_(V1) lines need to be removed from the vector lines that are in theInitializing stage, and the J_(V1) lines join in the vector lines thatare in the Showtime stage, that is, the S_(V2) at the t2 time is a unionset of the S_(V1) and the J_(V1). If no new vector line joins in but anynew legacy line joins in within the period from t1 to t2, the J_(V2) isan empty set but the J_(L2) is not an empty set, and the state needs tochange to S3.

In the S3 state, the VCE may select a group of lines T randomly from theJ_(L2) to perform further initializing, where the T needs to include aproper number of lines. Preferably, 1 or 2 lines may be selected forfurther initializing. In the period from the start of furtherinitializing of the T to the T fully entering the Showtime stage, it isnot allowed to initialize other lines. Control is exercised to performno further initializing for other lines that are in the initializingstate except the T until the T fully enters the Showtime stage. Thefar-end crosstalk coefficient C_(T-SV2) from the T to S_(V2) may beestimated before the T enters the Showtime stage, where the C_(T-SV2) isused in signal processing to eliminate the far-end crosstalk caused bythe T to the S_(V2). If the number of lines in the J_(L2) is greaterthan the number of lines in the T, in the process of furtherinitializing the T, the VCE controls the VTU-O corresponding to thelines unattributed to the T in the J_(L2) to obstruct furtherinitializing of the Legacy lines, and additionally, controls the VTU-Ocorresponding to the T lines to make the current T lines continue theinitializing process simultaneously. However, the line initializing mayfail. The line that fails in initializing may stay in the Initializingstate and re-initiate the initializing at proper time. To make thedescription brief, this embodiment assumes that all lines can beinitialized successfully. A person skilled in the art can know how tohandle the scenario of initializing failure according to thisembodiment.

In the process of initializing the T, no initializing of other lines isfinished. Therefore, the vector lines and the Legacy lines in theShowtime stage in the system do not change until initializing of the Tlines is finished and the T lines enter the Showtime stage.

After the T lines enter the Showtime stage, as against the t2 time, atthe t3 time, with the T removed from the non-vector lines that are inthe Initializing stage, the non-vector lines that are in theInitializing stage change to J_(L3); and, with the T added to thenon-vector lines that are in the Showtime stage, the non-vector linesthat are in the Showtime stage change to S_(L3). If all J_(L2) linesenter the Showtime stage at the t3 time and no new line joins in betweent2 and t3, that is, the J_(L3) is an empty set and the J_(V3) is anempty set, the state changes to the S1 state; if any lines exist in theJ_(L3) and the J_(V3) is an empty set, then according to the proceduredescribed above, a group of lines T that are in the Join In stage areselected to be further initialized, and the state remains at S3; and, ifa new line exists and the J_(V3) is not an empty set, the state changesto the S2 state.

As shown in FIG. 10, another example of supporting a non-vector lineaccording to an embodiment of the present invention includes thefollowing steps:

1001. The VCE determines the line sets S_(V), S_(L), J_(V), and J_(L) atthe current time.

At a specific time point, each line set in each stage may be determinedfirst. Each of the four sets may be empty, but at least one of J_(V) andJ_(L) is not empty. In the example in FIG. 10, it is assumed that noneof the four sets is empty. According to this embodiment, a personskilled in the art can easily obtain the processing procedure in thecase that one set or certain sets are empty. In this embodiment, it isassumed that after the S_(V), the S_(L), the J_(V), and the J_(L) aredetermined in 1001 and before the initializing of all lines in the J_(L)is finished in 1004, no new line joins in and waits for initializingwithin the period.

1002. Continue initializing the lines in the J_(L). A subset T of theJ_(L) may be selected, and further initializing for the T is performedunder control. Before the T enters the Showtime stage, the far-endcrosstalk coefficient from the T to the S_(V) is estimated, and the Tchanges the state to enter the Showtime stage after initializing isfinished. In the period after the initializing is continued for the Tand before the T enters the Showtime stage, other lines in the J_(L) areobstructed, that is, no further initializing is performed for otherlines in the J_(L) until the T fully enters the Showtime stage. Afterinitializing of the T is finished, the line set S_(L) is updated to aunion set of the S_(L) and the T determined in 1001, and the line setJ_(L) is updated to a set with the T removed from the original J_(L). Ifother lines still exist in the J_(L), the foregoing process in this stepis repeated until the J_(L) becomes an empty set.

To ensure the effect of initializing, the subset T selected each timeshould include a proper number of lines, and preferably, include 1 or 2lines.

1003. Continue the initializing process of the J_(V). In the process ofinitializing the

J_(V), estimate the far-end crosstalk coefficient from the J_(V) to theS_(V), the far-end crosstalk coefficient from the S_(V) to the J_(V),and the far-end crosstalk coefficient from the J_(V) to the J_(V), thatis, the far-end crosstalk coefficient between the J_(V) lines, where theJ_(V) enters the data transmission stage after initializing is finished.Update the line set, where the updated S_(V) is a union set of thebefore-update S_(V) and J_(V). When the far-end crosstalk coefficientbetween the vector lines is estimated, the crosstalk from the S_(L) lineto the J_(V) line may be treated as background noise.

1004. Estimate the far-end crosstalk coefficient from the S_(L) to theJ_(V), and update the line set J_(V) to an empty set.

The following describes specific application of the estimated far-endcrosstalk coefficient by using the scenario of supporting a non-vectorline in FIG. 10 as an example. After the far-end crosstalk coefficientfrom the T line to the S_(V) line is estimated in 1002, a precoderand/or an uplink crosstalk canceller may be enabled to cancel thecrosstalk from the S_(V) line to the T line. For the downlink direction,the following precoding is applied:{tilde over (x)} _(VS) =P _(VS-VS) x _(VS) +P _(LS-VS) x _(LS) +P_(T-VS) x _(T)

where P_(VS-VS), P_(LS-VS), and P_(T-VS) are downlink far-end crosstalkcoefficients from the S_(V) line, the S_(L) line, and the T line to theS_(V) line, respectively, P_(T-VS) is an estimated downlink far-endcrosstalk coefficient; x_(VS), x_(LS), and X_(T) are S_(V), S_(L), and Tline signals input into the precoder, respectively; and {tilde over(x)}_(VS) is a signal output by the precoder after the S_(V) line signalpasses through the precoder.

For the uplink direction, the crosstalk may be cancelled by using thefollowing method:{tilde over (y)} _(VS) =W _(VS-VS) y _(VS) +W _(LS-VS) y _(LS) +W_(T-VS) y _(T)

where W_(VS-VS) is an existing uplink far-end crosstalk coefficientbetween the S_(V) lines, y_(VS) is an S_(V) line signal input into thecanceller, W_(LS-VS) is an existing uplink far-end crosstalk coefficientfrom the S_(L) line to the S_(V) line, y_(LS) is an S_(L) line signalinput into the canceller, W_(T-VS) is an estimated uplink far-endcrosstalk coefficient from the T to the S_(V) line, y_(T) is a T linesignal input into the canceller, and {tilde over (y)}_(VS) is a signaloutput by the canceller after the S_(V) line signal passes through thecanceller.

After the far-end crosstalk coefficients from the J_(V) line to allS_(V) lines are estimated in 1003, a precoder and/or an uplink crosstalkcanceller may be enabled to cancel the crosstalk from the S_(V) line tothe J_(V) line, and a precoder and/or an uplink crosstalk canceller maybe enabled to cancel the crosstalk from the J_(V) line to the S_(V)line. In this case, the uplink and downlink cancellation of the S_(V)line is as follows:{tilde over (x)} _(VS) =P _(VS-VS) x _(VS) +P _(LS-VS) x _(LS) +P_(VJ-VS) x _(VJ); and{tilde over (y)} _(VS) =W _(VS-VS) y _(VS) +W _(LS-VS) y _(LS) +W_(VJ-VS) y _(VJ).

Because the far-end crosstalk coefficient from the S_(L) line to theJ_(V) is not estimated at the moment, the uplink and downlinkcancellation of the J_(V) line is as follows:{tilde over (x)} _(VJ) =P _(VS-VJ) x _(VS) +P _(VJ-VJ) x _(VJ); and{tilde over (y)} _(VJ) =W _(VS-VJ) y _(VS) +W _(VJ-VJ) y _(VJ).

After the far-end crosstalk coefficient from the S_(L) line to the J_(V)line and the far-end crosstalk coefficient from the J_(L) line to theJ_(V) line are estimated in 1004, a precoder and/or an uplink crosstalkcanceller may be enabled to cancel the crosstalk from the J_(V) line tothe S_(L) line, and a precoder and/or an uplink crosstalk canceller maybe enabled to cancel the crosstalk to the J_(L) line. In this case, theuplink and downlink cancellation of the J_(V) line is as follows:{tilde over (x)} _(VJ) =P _(VS-VJ) x _(VS) +P _(LS-VJ) x _(LS) +P_(VJ-VJ) x _(VJ); and{tilde over (y)} _(VJ) =W _(VS-VJ) y _(VS) +W _(LS-VJ) y _(LS) +W_(VJ-VJ) y _(VJ).

The meanings of the parameters in the above formulas may be obtainedaccording to the above description, and are not described hererepeatedly.

The VCE can implement a state machine to control initializing for newlines to support non-vector lines. The lines in the Showtime stage atany time constitute a set S, and new lines that are currently in theInitializing stage constitute a set J, where S includes a vector lineset S_(V) and a legacy line set S_(L), and J includes a vector line setJ_(V) and a legacy line set J_(L). The VCE may perform state transitionin a way shown in FIG. 11:

When the VCE is in the T1 state, the VCE updates the current state ofthe J regularly or irregularly, and performs state transition accordingto the state of the J: if the J is an empty set, that is, no linecurrently joins in and waits for getting online, the T1 state remains;if the J_(L) is not an empty set, that is, the J includes a legacy line,the state changes to the T2 state; if the J_(L) is an empty set and theJ_(V) is not an empty set, that is, the J includes only vector lines,the state changes to the T3 state.

It can be seen from the foregoing judgment for state transition that inthe state machine, when a vector line and a legacy line that are in theJoin In state coexist, the legacy line is initialized first.

When the VCE is in the T2 state, the legacy line in the Initializingstage is initialized. In the initializing process, a new line may joinin and need to be initialized. State transition may be performedaccording to the state of the J in the current system each time afterinitializing of at least one legacy line is finished: if the J is anempty set, the state changes to the T1 state; if the J_(L) is not anempty set, the T2 state remains; and, if the J_(L) is an empty set andthe J_(V) is not an empty set, the state changes to the T3 state.

When the VCE is in the T3 state, the vector line in the Initializingstage is initialized. In the initializing process, a new line may joinin and need to be initialized. State transition may be performedaccording to the state of the J in the current system each time afterinitializing of at least one vector line is finished: if the J is anempty set, the state changes to the T1 state; if the J_(L) is not anempty set, the state changes to the T2 state; and, if the J_(L) is anempty set and the J_(V) is not an empty set, the T3 state remains.

The following describes the state machine in FIG. 11 with reference to aspecific Example

After the system starts running, at the t0 time, no line joins in, andthe state machine runs in the T1 state; and, at the t1 time, a new linejoins in the lines that are in the Initializing stage, the value of theJ_(L) changes to J_(L1), and the value of the J_(V) changes to J_(V1),and therefore, the state changes to T2. The vector line in the Showtimestage at the t1 time is S_(V1).

In the T2 state, the VCE may select a group of lines T randomly from theJ_(L1) to perform further initializing, where the T needs to include aproper number of lines. Preferably, 1 or 2 lines may be selected forinitializing. In the period after the initializing is continued for theT and before the T enters the Showtime stage, the initializing processfor other lines needs to be obstructed, that is, no further initializingis performed for other lines that are already in the Initializing stage.Before the T enters the Showtime stage, the far-end crosstalkcoefficient C_(T-SV1) from the T to the vector line S_(V1) that iscurrently in the Showtime stage is estimated, where the C_(T-SV1) isused in signal processing to eliminate the far-end crosstalk caused bythe T to the S_(V1). After initializing is finished, the T enters thedata transmission stage. If the number of lines in the J_(L1) is greaterthan the number of lines in the T, in the period of initializing the T,the VCE controls the VTU-O corresponding to the lines unattributed tothe T in the J_(L1) to obstruct further initializing of the lines, andadditionally, controls the VTU-O corresponding to the T lines to makethe current T lines continue the initializing process simultaneously. Inaddition, in the period of initializing the T, the initializing ofJ_(V1) lines is also obstructed, that is, no further initializing isperformed for the J_(V1) lines.

In the process of initializing the T, no initializing of other lines isfinished. Therefore, the vector lines and the legacy lines in theShowtime stage in the system do not change until initializing of the Tlines is finished and the T lines enter the Showtime stage.

After the T lines enter the Showtime stage, as against the t1 time, atthe t2 time, with the T removed from the non-vector lines that are inthe Initializing stage, the non-vector lines that are in theInitializing stage change to J_(L2); and, with the T added in thenon-vector lines that are in the Showtime stage, the non-vector linesthat are in the Showtime stage change to S_(L2). If all J_(L1) linesenter the Showtime stage at the t2 time and no new line joins in betweent1 and t2, that is, the J_(L2) is an empty set and the J_(V2) is anempty set, the state changes to the T1 state; if any lines still existin the J_(L2), then according to the procedure described above, anothergroup of lines T that are in the Initializing stage are selected toundergo further initializing, and the state remains at T2; and, if theJ_(L2) becomes an empty set and the J_(V2) is not an empty set, thestate changes to the T3 state.

In the T3 state, the VTU-O corresponding to the J_(V2) lines iscontrolled so that the J_(V2) lines enter the initializing processsimultaneously. After initializing is finished, all J_(V2) lines enterthe Showtime stage.

If a vector line S_(V2) in the Showtime stage already exists in thesystem at the t2 time, in the process of initializing the J_(V2), thefar-end crosstalk coefficient C_(JV2-SV2) from the J_(V2) to the vectorline S_(V2) that is currently in the data transmission stage, thefar-end crosstalk coefficient C_(SV2-JV2) from the S_(V2) to the J_(V2),and the far-end crosstalk coefficient C_(JV2-JV2) between the J_(V2)lines may be estimated. The J_(V2) enters the Showtime stage afterinitializing is finished. The C_(JV2-SV2) is used in signal processingto eliminate the far-end crosstalk caused by the J_(V2) to the S_(V2),the C_(SV2-JV2) is used in signal processing to eliminate the far-endcrosstalk caused by the S_(V2) to the J_(V2), and the C_(JV2-JV2) isused in signal processing to eliminate the far-end crosstalk between theJ_(V2) lines.

In the process of initializing the J_(V2), the far-end crosstalkcoefficient C_(SL2-JV2) from the S_(L2) to the J_(V2) may be estimated,where the C_(SL2-JV2) is used in signal processing to eliminate thefar-end crosstalk caused by the S_(L2) to the J_(V2).

In the process of initializing the J_(V2), no initializing of otherlines is finished. Therefore, in the period from the t2 time to the timewhen initializing of the J_(V2) lines is finished and the J_(V2) linesenter the Showtime stage, the vector lines and the legacy lines in theShowtime stage in the system do not change.

After initializing of the J_(V2) lines is finished and the J_(V2) linesenter the Showtime stage, as against the t2 time, at the t3 time, theJ_(V2) lines are removed from the vector lines that are in the Join Instage, and the J_(V2) lines join in the vector lines that are in theShowtime stage, that is, the S_(V3) at the t3 time is a union set of theS_(V2) and the J_(V2). If a new legacy line joins in within the periodfrom t2 to t3, the J_(L3) is not an empty set and the state needs tochange to T2.

An embodiment of the present invention provides an apparatus forsupporting a non-vector line. As shown by 1200 in FIG. 12, the apparatusincludes:

a non-vector line selecting unit 1201, configured to select n non-vectorlines T_(L) from lines that are in an initializing stage, where n is aninteger greater than or equal to 1;

a non-vector line initializing controlling unit 1203, configured tocontrol to perform no further initializing for other lines that are inthe initializing stage except the T_(L) until the T_(L) fully enters adata transmission stage; and

a non-vector line far-end crosstalk coefficient estimating unit 1205,configured to estimate, before the T_(L) enters the data transmissionstage, a far-end crosstalk coefficient C_(TL-SV) from the T_(L) to avector line S_(V) that is in the data transmission stage, where theC_(TL-SV) is used in signal processing to eliminate far-end crosstalkcaused by the T_(L) to the S_(V).

Further, the apparatus shown by 1200 may include:

a vector line initializing unit 1207, configured to control toinitialize at least one vector line T_(V) in the lines that are in theinitializing stage; and

a vector line far-end crosstalk coefficient estimating unit 1209,configured to estimate, before the T_(V) enters the data transmissionstage, a far-end crosstalk coefficient C_(SL-TV) from the non-vectorline S_(L) that is currently in the data transmission stage to the T_(V)and a far-end crosstalk coefficient C_(TV-TV) between the lines Tv,where the C_(SL-TV) is used in signal processing to eliminate far-endcrosstalk caused by the S_(L) to the T_(V), and the C_(TV-TV) is used insignal processing to eliminate far-end crosstalk between the lines Tv.

The vector line far-end crosstalk coefficient estimating unit 1209 isfurther configured to estimate, before the T_(V) enters the datatransmission stage, a far-end crosstalk coefficient C_(TV-SV) from theT_(V) to the vector line S_(V) that is currently in the datatransmission stage and a far-end crosstalk coefficient C_(SV-TV) fromthe S_(V) to the T_(V), where the C_(TV-SV) is used in signal processingto eliminate far-end crosstalk caused by the T_(V) to the S_(V), and theC_(SV-TV) is used in signal processing to eliminate far-end crosstalkcaused by the S_(V) to the T_(V).

The apparatus shown by 1200 may be implemented on the VCE, and the VCEcontrols the VTU-O-v corresponding to the vector line and the VTU-O-lcorresponding to the legacy line in a unified manner so that the VTU-O-vand the VTU-O-l can perform the initializing process in a certain orderfor the lines connected to them, and can use the interfaces describedbelow to perform functions related to calculation of the far-endcrosstalk coefficient from the legacy line to the vector line. Throughuniform control exercised by the VCE, the legacy lines in theInitializing stage and/or the vector lines in the Initializing stagefinish the initializing process in a certain order.

In the embodiment of the present invention, the far-end crosstalkcoefficient from a non-vector line to a vector line needs to beestimated. To estimate the far-end crosstalk coefficient from the legacyline to the vector line, the symbol of the legacy line may besynchronized with the symbol of the vector line, which can be completedby the VTU-O by controlling alignment of downlink transmitted symbolsbetween the legacy line and the vector line. In the current VDSL2system, a proper timing advance TA (Timing Advance) value may be set toaccomplish the synchronization of uplink symbols received by the VTU-Obetween the legacy line and the vector line.

In addition, the VCE needs to control the legacy line and the vectorline in a unified manner, so as to control the initializing process ofthe legacy line and the initializing process of the legacy line and thevector line in a certain order, and estimate the far-end crosstalkcoefficient from the legacy line to the vector line accurately andquickly to the utmost.

In addition, to estimate the far-end crosstalk coefficient from thelegacy line to the vector line accurately to the utmost, the signalssent by the legacy line on the Sync Symbol of the vector line should berandomized to the utmost.

However, on the Sync Symbol of the legacy line, the legacy linemodulates a synchronization frame composed of all 0s or all 1s. Thesynchronization frame turns over, that is, changes from all 0s to all 1sor from all 1s to all 0s only when it is used to mark a valid timestampof online reconfiguration sent by a peer VTU, and therefore, thedownlink signals sent or the uplink signals received by the legacy lineon its Sync Symbol are deficiently randomized In the downlink direction,to avoid using the deficiently randomized signals that are sent by thelegacy line on its Sync Symbol, the VCE may control positions of theSync Symbol of the legacy line in the downlink direction in a unifiedmanner to accomplish non-alignment between the Sync Symbol of the legacyline and the Sync Symbol of the vector line (the Sync Symbol positionsof all vector lines are the same). In the uplink direction, the VCE canhardly control non-alignment between the Sync Symbol of the legacy lineand the Sync Symbol of the vector line.

No matter whether the VCE controls the downlink or uplink Sync Symbolpositions of the legacy line to prevent the Sync Symbol from aligningwith the downlink or uplink Sync Symbol of the vector line in the samedirection, the embodiment of the present invention will demonstrate thatunder non-forced control, that is, under the condition that the SyncSymbol of the legacy line is aligned with any one of the 257 symbols,namely, 256 data symbols and 1 Sync Symbol, in a hyperframe of thevector line at equal probability, the Sync Symbol of the legacy line isnot aligned with the Sync Symbol of the vector line in a majority ofcircumstances in the downlink direction and/or uplink direction. In thiscase, the frequency domain signal existent on the legacy line andcorresponding to the time point of the Sync Symbol of the vector linemay be a sync symbol or a data symbol, without being forced to be anon-sync symbol.

For either the downlink direction or the uplink direction, the VDSL2 andthe vectored-DSL system insert a Sync Symbol every other 256 datasymbols cyclically, the time length of the Data Symbols is equal to thetime length of the Sync Symbols, and the Sync Symbols of all vectoredDSLs keep aligned. Therefore, for any direction, when the total numberof legacy lines in the Showtime stage, the Initializing stage, and theJoin In stage in the current system is N, the probability P_(k) ofalignment between the Sync Symbols of k or more legacy lines and theSync Symbols of the vector lines is:

$P_{k} = {\sum\limits_{i = k}^{N}\;{C_{N}^{i} \cdot \left( \frac{1}{257} \right)^{i} \cdot \left( \frac{256}{257} \right)^{N - i}}}$

Through calculation, the following table is obtained:

N P₂ P₃ 39 10.2‰ 0.48‰ 50 16.4‰   1‰ 92 50.3‰  5.7‰ 100 58.3‰  7.2‰ 11372.2‰   10‰ 137 100.1‰  16.8‰ 150 116.3‰  21.3‰ 200 183.2‰    44‰

Firstly, the deficient randomization of the signals sent on the alignedSync Symbols of the legacy lines can affect the precision of estimatingthe far-end crosstalk coefficient from the legacy lines to the vectorlines only when the Sync Symbols in any direction of two or more legacylines are aligned with the Sync Symbols of the vector lines. As seenfrom the above table, when the number of the legacy lines in the currentsystem is not greater than 100, the probability of the foregoing effectis not greater than 6%; and, when the number of the legacy lines in thecurrent system is not greater than 50, the probability of the foregoingeffect is not greater than 2%. Therefore, it can be obtained from theforegoing analysis that the alignment between the Sync Symbols of two ormore legacy lines and the Sync Symbols of the vector lines is alow-probability event.

Secondly, if the Sync Symbols of k (k is greater than or equal to 2)legacy lines are aligned with the Sync Symbol of the vector line, theprecision on K columns will be affected when the VCE estimates thecrosstalk channel coefficient from the legacy line to the vector line.With reference to the probability analysis, if N legacy lines exist inthe system, the number K of columns whose crosstalk channel coefficientprecision is affected on average is:

$\begin{matrix}{K = {\sum\limits_{i = 2}^{N}\;\left\lbrack {C_{N}^{i} \cdot \left( \frac{1}{257} \right)^{i} \cdot \left( \frac{256}{257} \right)^{N - i} \cdot i} \right\rbrack}} \\{= {{\sum\limits_{i = 1}^{N}\;\left\lbrack {C_{N}^{i} \cdot \left( \frac{1}{257} \right)^{i} \cdot \left( \frac{256}{257} \right)^{N - i} \cdot i} \right\rbrack} - {C_{N}^{1} \cdot \left( \frac{1}{257} \right)^{1} \cdot \left( \frac{256}{257} \right)^{N - 1} \cdot 1}}} \\{= {{\frac{N}{257} \cdot {\sum\limits_{i = 1}^{N}\;\left\lbrack {C_{N - 1}^{i - 1} \cdot \left( \frac{1}{257} \right)^{i - 1} \cdot \left( \frac{256}{257} \right)^{N - 1 - {({i - 1})}}} \right\rbrack}} - {\frac{N}{257} \cdot \left( \frac{256}{257} \right)^{N - 1}}}} \\{= {{\frac{N}{257} \cdot {\sum\limits_{j = 0}^{N - 1}\;\left\lbrack {C_{N - 1}^{j} \cdot \left( \frac{1}{257} \right)^{j} \cdot \left( \frac{256}{257} \right)^{N - 1 - j}} \right\rbrack}} - {\frac{N}{257} \cdot \left( \frac{256}{257} \right)^{N - 1}}}} \\{= {\frac{N}{257} - {\frac{N}{257} \cdot \left( \frac{256}{257} \right)^{N - 1}}}} \\{= {\frac{N}{257} \cdot \left\lbrack {1 - \left( \frac{256}{257} \right)^{N - 1}} \right\rbrack}}\end{matrix}$

For a total number N of legacy lines, the average number of affectedcolumns K is as follows:

N K 30 0.0125 50 0.0338 100 0.1246 150 0.2572 200 0.4200 347 0.9998 3481.0040

As seen from the above table, when the total number of legacy lines isnot greater than 347, the number of columns with the precision ofestimating the crosstalk channel coefficient affected is less than 1 onaverage. In practical application, in view of the system supportingcapacity, the total number of accessed users, the allocation of allusers using the non-vectored ordinary VDSL2 services and thevectored-DSL service, and the online convergence ratio of users who usethe ordinary VDSL2 services, N is generally not greater than 50.

Thirdly, by using a proper estimation method such as the least meansquare (LMS) error algorithm, the rate of the vector lines can still beincreased by using the estimated far-end crosstalk coefficient.

In summary, even if the VCE does not control whether the Sync Symbol ofthe legacy line in any direction is aligned with the Sync Symbol of thevector line or not, that is, no control is exercised on the alignmentbetween the Sync Symbol of the legacy line and the Sync Symbol of thevector line, it is scarcely possible that the Sync Symbols of two ormore legacy lines are aligned with the Sync Symbol of the vector line,and, when the VCE estimates the far-end crosstalk coefficient from suchlegacy lines to the vector line, only the precision extent is affected.On average, when the total number of lines in the system is not greaterthan 347, the number of columns with the precision of estimating thecrosstalk channel coefficient affected is less than 1. Therefore, byapplying the embodiment of the present invention, in any direction, theVCE can still estimate the far-end crosstalk coefficient from the legacyline to the vector line effectively.

FIG. 13 shows a vectored-DSL system according to an embodiment of thepresent invention:

The system includes n vector lines, where n is greater than or equalto 1. The VTU-O corresponding to vector line k (k=1, . . . , n) isdenoted by VTU-O-v_(k). The VCE is connected to the VTU-O-v_(k) throughan interface ε-c-y_(k) and controls the VTU-O-v_(k).

The VTU-O of each vector line is connected to the VTU-O of other vectorlines, where the VTU-O-v_(i) corresponding to line i (i=1, . . . , n) isconnected to the VTU-O-v_(j) corresponding to line j (j=1, . . . , n;j≠i) through an interface ε-v_(i)-v_(j), and transmits the signals ofline i to cancel the crosstalk of line j.

The system includes m legacy lines, where m is greater than or equalto 1. The VTU-O corresponding to legacy line k (k=1, . . . , m) isdenoted by VTU-O-l_(k). The VCE is connected to the VTU-O-l_(k) throughan interface ε-c-l_(k) and controls the VTU-O-l_(k); and the VCEcontrols the legacy line through the VTU-O-l_(k).

The VCE does not control whether the Sync Symbol of the legacy line isaligned with the Sync Symbol of the vector line, and the VTU-O-l_(k)transmits a sent signal and a received signal of the legacy line in thefrequency domain at the Sync Symbol time point of the vector line to theVCE through the interface ε-c-l_(k).

The VTU-O-v_(i) sends an error sample of the Sync Symbol of each vectorline to the VCE through the interface ε-c-v_(i) (i=1, . . . , n).

The VCE estimates the far-end crosstalk coefficient from the legacy lineto the vector line by using the sent signal and the received signal ofthe legacy line in the frequency domain at the Sync Symbol time point ofthe vector line and the error sample corresponding to the Sync Symbol ofthe vector line.

The VCE sends the estimated far-end crosstalk coefficient to thecorresponding VTU-O-v_(i) through the interface ε-c-v_(i) (i=1, . . . ,n).

The VTU-O of each legacy line interacts with the VTU-O of each vectorline, where the interface between the VTU-O-l_(i) corresponding tolegacy line i (i=1, . . . , m) and the VTU-O-v_(j) corresponding tovector line j (j=1, . . . , n) is ε-l_(i)-v_(j), and the VTU-O-l_(i)transmits the sent signal and the received signal in the frequencydomain on legacy line i to the VTU-O-v_(j) through the interfaceε-l_(i)-v_(j).

The VTU-O-v_(i) uses the received far-end crosstalk coefficient and thesent signal and the received signal in the frequency domain on legacyline i to cancel the far-end crosstalk from the legacy line to thevector line.

The VTU-O-v_(i) (i=1, . . . , n) uses the ε-c-v_(i) interface and theVTU-O-l_(j) (j=1, . . . , m) uses the ε-c-l_(j) interface to report tothe VCE whether the CPE used by the connected line is a vectored CPEthat supports the vectored-DSL standard or a legacy CPE that does notsupport the vectored-DSL standard. The VCE can identify the informationreported by the VTU-O, that is, the information indicating whether theCPE supports the vectored-DSL standard.

Through the interface ε-c-v_(i) (i=1, . . . , n) and the interfaceε-c-l_(j) (j=1, . . . , m), the VCE controls synchronization between thedownlink symbol sent by the VTU-O-v_(i) of vector line i and thedownlink symbol sent by the VTU-O-l_(j) of legacy line j.

According to the information, through the interface ε-c-v_(i) (i=1, . .. , n) and the interface ε-c-l_(j) (j=1, . . . , m), the VCE controlsnon-alignment between the downlink Sync Symbol sent by the VTU-O-v_(j)of the vector line i and the downlink Sync Symbol sent by theVTU-O-l_(j) of legacy line j. The VTU-O may also be used to controlnon-alignment between the uplink Sync Symbol sent by the remote-endvector transceiver unit VTU-R (Vector Transceiver Unit at Remote) of thelegacy line and the uplink Sync Symbol sent by the VTU-R of the vectorline.

An embodiment of the present invention provides a method for estimatinga far-end crosstalk coefficient. The method is used to estimate afar-end crosstalk coefficient of crosstalk caused by a legacy line to avector line. As shown by 1400 in FIG. 14, the method includes thefollowing steps:

1401. Perform no control on alignment between a Sync Symbol of a legacyline and a Sync Symbol of a vector line, and receive a signal of eachlegacy line, where the signal is an uplink sync symbol or a data symbolthat is in a frequency domain and corresponds to a time point of anuplink Sync Symbol of the vector line, or is a sync symbol or a datasymbol that is in the frequency domain and corresponds to a time pointof a downlink Sync Symbol of the vector line, or is the uplink signaland the downlink signal.

For either the downlink direction or the uplink direction in 1401, nocontrol is performed for alignment or non-alignment between the SyncSymbol of the legacy line and the Sync Symbol of the vector line, andtherefore, the signal may be a Sync Symbol or a Data Symbol.

1403. Receive an error sample of each vector line, where the errorsample is an uplink error sample corresponding to the uplink Sync Symbolof the vector line, or a downlink error sample corresponding to thedownlink Sync Symbol of the vector line, or the uplink error sample andthe downlink error sample.

1405. Use the signal and the error sample to calculate the far-endcrosstalk coefficient from each legacy line to each vector line, wherethe far-end crosstalk coefficient is an uplink far-end crosstalkcoefficient, or a downlink far-end crosstalk coefficient, or both theuplink far-end crosstalk coefficient and the downlink far-end crosstalkcoefficient; the uplink signal and the uplink error sample are used toestimate the uplink far-end crosstalk coefficient; and the downlinksignal and the downlink error sample are used to estimate the downlinkfar-end crosstalk coefficient.

In calculating the far-end crosstalk coefficient in 1405, algorithmssuch as a least mean square error LMS (Least Mean Square) algorithm, amatrix first-order likelihood algorithm, or a matrix inversion algorithmmay be applied.

In the above embodiment, without upgrading the existing CPE of thelegacy line, the far-end crosstalk coefficient from the non-vector lineto the vector line can be estimated when no alignment control isperformed on the Sync Symbol of the non-vector line and the Sync Symbolof the vector line to force non-alignment or alignment between the two.In this way, the far-end crosstalk from the non-vector line to thevector line is eliminated to the utmost by using the estimated crosstalkcoefficient, and the vector-DSL system instability caused by the legacyline is thereby reduced to the utmost.

An embodiment of the present invention provides an apparatus forestimating a far-end crosstalk coefficient, where a schematic diagram ofthe structure of the apparatus is shown by 1500 in FIG. 15. TheVTU-O-l_(i) corresponding to legacy line i (i=1, . . . , m) transmits asignal of the non-vector line to the VCE through the interfaceε-c-l_(i), without controlling whether the sync symbol of the non-vectorline is aligned with the sync symbol of the vector line. The signal isan uplink signal that is in a frequency domain and corresponds to a timepoint of an uplink sync symbol of the vector line, or is a downlinksignal that is in the frequency domain and corresponds to a time pointof a downlink sync symbol of the vector line, or is the uplink signaland the downlink signal. The signal is received by a signal receivingunit 1501 of the VCE.

The VTU-O-v_(i) corresponding to the vector line i (i=1, . . . , n)transmits the error sample of the vector line to the VCE through theinterface ε-c-v_(i), where the error sample is an uplink error samplecorresponding to the uplink sync symbol of the vector line, or is adownlink error sample corresponding to the downlink sync symbol of thevector line, or is the uplink error sample and the downlink errorsample. The error sample is received by an error receiving unit 1503 ofthe VCE.

In the calculating unit 1505, the VCE uses the received signal and errorsample to calculate the far-end crosstalk coefficient from the legacyline to the vector line.

An embodiment of the present invention provides a VTU-O of a vectorline. As shown in FIG. 16, the VTU-O includes:

a sending unit 1601, configured to send an error sample of the vectorline, where the error sample is an uplink error sample corresponding tothe uplink sync symbol of the vector line, or a downlink error samplecorresponding to the downlink sync symbol of the vector line, or theuplink error sample and the downlink error sample;

a coefficient receiving unit 1603, configured to receive the far-endcrosstalk coefficient from the legacy line to the line, where thefar-end crosstalk coefficient is an uplink far-end crosstalk coefficientor a downlink far-end crosstalk coefficient, or both an uplink far-endcrosstalk coefficient and a downlink far-end crosstalk coefficient;

a signal receiving unit 1605, configured to receive a signal thatincludes data symbols and sync symbols from the legacy line, where thesignal is an uplink signal, or a downlink signal, or an uplink anddownlink signal; and

a cancelling unit 1607, configured to use the far-end crosstalkcoefficient and the signal to cancel interference caused by the far-endcrosstalk to the vector line.

An embodiment of the present invention provides a VTU-O of a legacyline. As shown by 1700 in FIG. 17, the VTU-O includes:

a first sending unit 1701, configured to send a first signal of a legacyline, where the first signal is an uplink signal that is in a frequencydomain and corresponds to a time point of an uplink Sync Symbol of avector line, or is a downlink signal that is in the frequency domain andcorresponds to a time point of a downlink Sync Symbol of the vectorline, or is the uplink signal and the downlink signal, and the firstsignal is a signal in a circumstance that no control is exercised onwhether the Sync Symbol of the non-vector line is aligned with the syncsymbol of the vector line;

a second sending unit 1703, configured to send a second signal of thelegacy line, where the second signal is a downlink signal, or an uplinksignal, or an uplink and downlink signal, and the uplink signal and thedownlink signal include a data symbol and a sync symbol.

After the crosstalk coefficient is estimated, the VCE transmits theestimated far-end crosstalk coefficient to the VTU-O-v_(i) correspondingto vector line i through the interface ε-c-v_(i) (i=1, . . . , n).

FIG. 18 shows a scenario of cancelling downlink crosstalk in a systemaccording to an embodiment of the present invention. Each cancellingunit cancels crosstalk generated by their respective line. A cancellingunit i (i=1, . . . , n) is used to cancel crosstalk on vector line i.The cancelling unit i may be located in the VTU-O-v_(i) and thecancelling unit is an (n+m)×1 cancelling unit, and, by using signalsthat include all vector line signals and all legacy line signals, and acancellation coefficient from all lines that include all vector linesand all legacy lines to vector line i, perform the following crosstalkcancellation, that is, perform a multiplication and summation operation:

$X_{vi}^{\prime} = {{\sum\limits_{j = 1}^{n}\;{p_{{vj} - {vi}}X_{vj}}} + {\sum\limits_{j = 1}^{m}\;{p_{{lj} - {vi}}X_{lj}}}}$

where p_(Vj-vi) is a far-end crosstalk coefficient from vector line j tovector line i, p_(lj-vi) is a far-end crosstalk coefficient from legacyline j to vector line i, X_(Vj) is signal data input from vector line jinto the canceller, X_(lj) is signal data input from legacy line j intothe canceller, X′_(vi) is signal data output by the canceller of vectorline i, and p_(vi-vi) may be set to 1 or another value. All n cancellingunits form a canceller that is in a matrix form:{tilde over (x)} _(V) =P _(V-V) x _(V) +P _(L-V) x _(L)

where P_(V-V) is a far-end crosstalk coefficient between the vectorlines, P_(L-V) is a far-end crosstalk coefficient from a legacy line toa vector line, x_(V) is signal data input from the vector line into thecanceller, x_(L) is signal data input from the legacy line into thecanceller, and {tilde over (x)}_(V) is signal data output by thecanceller of the vector line.

The VCE transmits the calculated far-end crosstalk coefficient from thelegacy line to the vector line to the VTU-O corresponding to the vectorline through the interface ε-c-v_(k) (k=1, . . . , n), denoted by ε-c.

Between the VTU-Os corresponding to the vector line, the i^(th) (i=1, .. . , n) VTU-O-v_(i) is connected to the j^(th) (j=1, . . . , n; j≠i)VTU-O-v_(j) through the interface ε-v_(i)-v_(j), and transmits thei^(th) line signal to the j^(th) line to cancel crosstalk of the j^(th)line.

Through the interface ε-l_(i)-v_(j) (i=1, . . . , m, j=1, . . . , n),the VTU-O-l_(J) transmits the sent signal and the received signal in thefrequency domain of the i^(th) legacy line to the VTU-O-v_(j) to cancelthe crosstalk from the legacy line to the vector line. The VTU-O-v_(j)uses the signals and the far-end crosstalk coefficient from the legacyline to the vector line to cancel the crosstalk of the legacy line.

The k^(th) interface ε-v_(k) (k=1, . . . , n) aggregates signals forcrosstalk cancellation of m interfaces ε-l_(i)-y_(k) (i=1, . . . , m)and n−1 interfaces ε-v_(j)-v_(k) (j=1, . . . , n; j≠k), where thesignals are used to cancel crosstalk within the canceller.

FIG. 18 shows an example of a downlink scenario. An uplink scenario canbe easily inferred by a person skilled in the art according to thedownlink scenario.

In the embodiment of the present invention, without upgrading the VDSL2legacy CPE in the live network of the VDSL2, the vectored-DSL system canselect some non-vector lines for initializing, and perform no furtherinitializing for other lines in the process of initializing the selectednon-vector lines, thereby controlling orderly initializing of legacylines. Meanwhile, the interference caused by initializing of other linesonto the initializing of the selected line can be reduced. In estimatingthe far-end crosstalk coefficient, a better estimation result can beachieved, and therefore, the existing VDSL legacy CPE in the livenetwork is supported, the crosstalk from the legacy line to the vectorline in the downlink direction and the crosstalk from the legacy line tothe vector line in the uplink direction are cancelled to the utmost, andthe impact caused by the legacy line onto stability of the vector linein the entire vectored-DSL system is reduced to the utmost.

Through the foregoing description of the embodiments, a person skilledin the art is clearly aware that the present invention may beimplemented through software in addition to a necessary hardwareplatform, or all through hardware. Based on such an understanding, allor a part of the technical solutions of the present inventioncontributing to the prior art may be implemented in a form of a softwareproduct. The computer software product may be stored in a storagemedium, such as a ROM/RAM, a magnetic disk, and an optical disk, andinclude several instructions for instructing a computer device (whichmay be a personal computer, a server, or a network device) to performthe methods described in each embodiment or certain parts of theembodiments of the present invention.

The foregoing descriptions are merely exemplary specific embodiments ofthe present invention, but are not intended to limit the protectionscope of the present invention. Any variation or replacement readilyfigured out by a person skilled in the art within the technical scopedisclosed in the present invention shall fall within the protectionscope of the present invention. Therefore, the protection scope of thepresent invention shall be subject to the protection scope of theclaims.

What is claimed is:
 1. A method for supporting a non-vector line,comprising: selecting n non-vector lines T_(L) from a plurality of linesthat are in an initializing stage, wherein n is an integer greater thanor equal to 1; controlling to perform no further initializing for otherlines that are in the initializing stage except the T_(L) until theT_(L) fully enters a data transmission stage; and before the T_(L)enters the data transmission stage, estimating a far-end crosstalkcoefficient C_(TL-SV) from the T_(L) to a vector line S_(V) that is inthe data transmission stage including: performing no control onalignment between a sync symbol of the non-vector line and a sync symbolof the vector line, and receiving a frequency domain signal existent onthe T_(L) and corresponding to a time point of the sync symbol of thevector line; receiving an error sample of the sync symbol of the S_(V);and using the signal and the error sample to calculate the C_(TL-SV),wherein the C_(TL-SV) is used in signal processing to eliminate far-endcrosstalk caused by the T_(L) to the S_(V).
 2. The method according toclaim 1, wherein: before the T_(L) enters the data transmission stage,the estimating a far-end crosstalk coefficient C_(TL-SV) from the T_(L)to a vector line S_(V) that is in the data transmission stage furthercomprises: in only a channel discovery stage of the T_(L) initializingprocess, estimating the far-end crosstalk coefficient C_(TL-SV) from theT_(L) to the vector line S_(V) that is in the data transmission stage;or in the channel discovery stage and a training stage of the T_(L)initializing process, estimating twice the far-end crosstalk coefficientC_(TL-SV) from the T_(L) to the vector line S_(V) that is in the datatransmission stage.
 3. The method according to claim 1, furthercomprising: controlling to initialize at least one vector line T_(V) inthe plurality of lines that are in the initializing stage; and beforethe T_(V) enters the data transmission stage, estimating a far-endcrosstalk coefficient C_(SL-TV) from the non-vector line S_(L) that isin the data transmission stage to the T_(V) and a far-end crosstalkcoefficient C_(TV-TV) between the lines Tv, wherein the C_(SL-TV) isused in signal processing to eliminate far-end crosstalk caused by theS_(L) to the T_(V), and the C_(TV-TV) is used in signal processing toeliminate far-end crosstalk between the lines Tv.
 4. The methodaccording to claim 3, wherein: before the T_(V) enters the datatransmission stage, the method comprises: being in a training stage ofthe T_(V) initializing process.
 5. The method according to claim 3,wherein the estimating a far-end crosstalk coefficient C_(SL-TV) fromthe non-vector line S_(L) that is in the data transmission stage to theT_(V) comprises: performing no control on alignment between a syncsymbol of the non-vector line and a sync symbol of the vector line, andreceiving a frequency domain signal existent on the S_(L) andcorresponding to a time point of the sync symbol of the vector line;receiving an error sample of the sync symbol of the T_(V); and using thesignal and the error sample to calculate the C_(SL-TV).
 6. The methodaccording to claim 3, further comprising: before the T_(V) enters thedata transmission stage, estimating a far-end crosstalk coefficientC_(TV-SV) from the T_(V) to the vector line S_(V) that is in the datatransmission stage and a far-end crosstalk coefficient C_(SV-TV) fromthe S_(V) to the T_(V), wherein the C_(TV-SV) is used in signalprocessing to eliminate far-end crosstalk caused by the T_(V) to theS_(V), and the C_(SV-TV) is used in signal processing to eliminatefar-end crosstalk caused by the S_(V) to the T_(V).
 7. The methodaccording to claim 1, wherein the controlling to perform no furtherinitializing for other lines that are in the initializing stage exceptthe T_(L) comprises: controlling an optical network unit-side VDSL2transceiver unit VTU-O not to send a handshake signal to other lines;or, controlling a VTU-O to prevent other lines from entering a channeldiscovery stage or staying in the channel discovery stage.
 8. Anapparatus for supporting a non-vector line, comprising: at least oneprocessor including: a non-vector line selector, configured to select nnon-vector lines T_(L) from a plurality of lines that are in aninitializing stage, wherein n is an integer greater than or equal to 1;a non-vector line initializing controller, configured to control toperform no further initializing for other lines that are in theinitializing stage except the T_(L) until the T_(L) fully enters a datatransmission stage; and a non-vector line far-end crosstalk coefficientestimator, configured to estimate, before the T_(L) enters the datatransmission stage, a far-end crosstalk coefficient C_(TL-SV) from theT_(L) to a vector line S_(V) that is in the data transmission stageincluding: a signal receiver, configured to receive, without performingcontrol on alignment between a sync symbol of the non-vector line and async symbol of the vector line, a frequency domain signal existent onthe T_(L) and corresponding to a time point of the sync symbol of thevector line; an error receiver, configured to receive an error sample ofthe sync symbol of the S_(V); and a calculator, configured to use thesignal and the error sample to calculate the C_(TL-SV), wherein theC_(TL-SV) is used in signal processing to eliminate far-end crosstalkcaused by the T_(L) to the S_(V).
 9. The apparatus according to claim 8,further comprising: a vector line initializer, configured to control toinitialize at least one vector line T_(V) in the plurality of lines thatare in the initializing stage; and a vector line far-end crosstalkcoefficient estimator, configured to estimate, before the TV enters thedata transmission stage, a far-end crosstalk coefficient C_(SL-TV) fromthe non-vector line S_(L) that is in the data transmission stage to theT_(V) and a far-end crosstalk coefficient C_(Tv-TV) between the linesTv, wherein the C_(SL-TV) is used in signal processing to eliminatefar-end crosstalk caused by the S_(L) to the T_(V), and the C_(TV-TV) isused in signal processing to eliminate far-end crosstalk between thelines Tv.
 10. The apparatus according to claim 9, wherein the vectorline far-end crosstalk coefficient estimator is further configured toestimate, before the T_(V) enters the data transmission stage, a far-endcrosstalk coefficient C_(TV-SV) from the T_(V) to the vector line S_(V)that is in the data transmission stage and a far-end crosstalkcoefficient C_(SV-TV) from the S_(V) to the T_(V), wherein the C_(TV-SV)is used in signal processing to eliminate far-end crosstalk caused bythe T_(V) to the S_(V), and the C_(SV-TV) is used in signal processingto eliminate far-end crosstalk caused by the S_(V) to the T_(V).
 11. Asystem for supporting a non-vector line, comprising: a vectoring controlentity VCE; at least two lines; an ONU-side vector transceiver unitVTU-O-v; and an ONU-side vector transceiver unit VTU-O-l, wherein: theat least two lines comprise at least one vector line and at least onenon-vector line, wherein the at least one vector line is connected tothe VTU-O-v and controlled by the VTU-O-v, and the at least onenon-vector line is connected to the VTU-O-l and controlled by theVTU-O-l; the VCE selects n non-vector lines T_(L) from a plurality oflines that are in an initializing stage, wherein n is an integer greaterthan or equal to 1; the VCE controls ONU-side vector transceiver unitscorresponding to other lines that are in the initializing stage exceptthe T_(L), so as to perform no further initializing for the other linesuntil the T_(L) fully enters a data transmission stage; and before theT_(L) enters the data transmission stage, the VCE estimates a far-endcrosstalk coefficient C_(TL-SV) from the T_(L) to a vector line S_(V)that is in the data transmission stage, wherein the C_(TL-SV) is used insignal processing to eliminate far-end crosstalk caused by the T_(L) tothe S_(V) including: performing, by the VCE, no control on alignmentbetween a sync symbol of the non-vector line and a sync symbol of thevector line, and transmitting, by the VTU-O-l, a frequency domain signalexistent on the TL and corresponding to a time point of the sync symbolof the vector line to the VCE; transmitting, by the VTU-O-v, an errorsample of the sync symbol of the SV to the VCE; and using, by the VCE,the signal and the error sample to calculate the CTL-SV.